The objective of the proposed study is to use two systems of malaria for characterization of selected potential functional antigens. The first system is P. lophurae. Recent evidence indicates the special importance of erythrocytic and exoerythrocytic merozoites in stimulating stage-specific immunity to malaria. Since methods are already available for the preparation of both types of these merozoites from P. lophurae, it is proposed to investigate in a comparative manner (a) the chemical nature and immunological properties of their polar organelles and (b) the immmunogenicity of their surface constituents. The second system is P. falciparum. In a recent study we showed that the knob-like protrusions that develop on erythrocyte membranes of P. falciparum infected erythrocytes are antigenically different from normal erythrocyte membranes. It is proposed to isolate the biochemical constituent(s) of these knobs and test them as potential functional antigens.